1. Field of the Invention
The present invention relates to an alignment method for aligning a photomask with an object to be exposed having a pattern arranged in a matrix with a long side in at least a portion thereof and conveyed in a direction of the long side, and more particularly to an alignment method, an alignment apparatus, and an exposure apparatus capable of performing highly accurate alignment for a pattern having a complex shape.
2. Description of Related Art
In this type of conventional alignment method, an imaging device having a plurality of light-receiving elements arranged in a straight line in a direction orthogonal to a conveying direction of a color filter substrate, captures an image of a plurality of rectangular pixels formed on a color filter substrate (object to be exposed), detects the position of a left side edge portion of a left-end pixel of the color filter substrate based on brightness information of the captured image, calculates the amount of position displacement between the position of the left side edge portion of the left-end pixel and a reference position (target position) preset in the imaging device, and move a photomask in the direction orthogonal to the conveying direction of the color filter substrate so as to correct the amount of position displacement to thereby perform an alignment between the photomask and the color filter substrate (for example, see Japanese Laid-Open Patent Publication No. 2008-76709).
In the conventional alignment method, however, a position at which brightness changes from dark level to bright level is detected, and based on the detected position, the pattern of the object to be exposed and the openings of the photomask are aligned. Therefore, in the conventional alignment method, for a pattern having a simple rectangular shape, it is easy to detect a reference position set on the edge portion of the pattern and to further perform the alignment, however, for a pattern having a complex shape such as a wiring patterns within pixels, for example, a TFT substrate, it is difficult to detect a reference position set on the edge portion of the pattern of complex shape, and to further perform the alignment. Therefore, it is difficult to perform the alignment between the pattern of the object to be exposed and the openings of the photomask with high accuracy.